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One of the uses of tamoxifen in the lab is the activation of enzymes deactivated via an estrogen-binding domain, like Cre-ERT (Cre-LBD). Tamoxifen is an estrogen analogue that binds with higher affinity than estrogen to altered estrogen binding domains.

Tamoxifen is administered to mice in 2 main ways: via the drinking water or in an oily mix given via a feeding needle. Administration via the drinking water is easier but somewhat less reliable.

Heat to 37°C before administration. Verify that tamoxifen is properly dissolved.

Feed orally to mice with a feeding needle. Fix the mice at their neck and ridge so that the belly is directed to the floor. Hold the mouse tightly so that it can not move the head, but not too tight to avoid choking. Carefully introduce the feeding needle in the mouth behind the tongue (max. 1 cm). It is helpful to mark 1 cm on the needle with an edding pen in order to see how deep you have inserted the needle.

Introduce slowly 50 μl of the Tamoxifen solution with the syringe. Make sure that they swallow (can be seen).